K. A. Mauritz et al., Polym. Mater. Sci. Eng. 58, 1079-1082 (1988), in an article titled "Nafion-based Microcomposites: Silicon Oxide-filled Membranes", discuss the formation of micro composite membranes by the growth of silicon oxide microclusters or continuous silicon oxide interpenetrating networks in pre-swollen "NAFION.RTM." sulfonic acid films. NAFION.RTM. is a registered trademark of E. I. du Pont de Nemours and Company.
U.S. Pat. No. 4,038,213 discloses the preparation of catalysts comprising perfluorinated ion-exchange polymers containing pendant sulfonic acid groups on a variety of supports.
The catalyst utility of perfluorinated ion-exchange polymers containing pendant sulfonic acid groups, supported and unsupported has been broadly reviewed: G. A. Olah et al., Synthesis, 513-531 (1986) and F. J. Waller, Catal. Rev.-Sci. Eng., 1-12 (1986).
WO 95/19222 describes a porous microcomposite comprising a perfluorinated ion-exchange microcomposite containing pendant sulfonic acid and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide. These catalysts are differentiated from NAFION.RTM. supported catalysts in that by virtue of the preparation of the microcomposite catalyst, the polymer becomes intimately mixed with a metal oxide precursor in solution, and thus becomes thoroughly entrapped and highly dispersed throughout a resulting network of metal oxide. With the polymer being mechanically entrapped within the metal oxide network and not merely on the surface of a support, as is the case in supported catalysts, the catalytic activity of these microcomposite catalysts is significantly increased.
R. S. Drago et al., in "Preparation and Catalytic Activity of a New Solid Acid Catalyst", J. Am. Chem. Soc. 110, 3311-3312, 1988 describe the preparation of a catalyst prepared by reacting an inorganic oxide with aluminum chloride in refluxing carbon tetrachloride. Results suggested that over 90% of the chloroaluminum species on the support had the composition (--O--)AlCl.sub.2.
Although a variety of reactions can be beneficially catalyzed by the compounds and the composites cited above, there is still a need for catalysts of increased activity and selectivity and useful in a broad range of applications.